Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$54.60	8.237%	$59.0974	$59.10	$59.10	$59.10
Purchase #2	$68.89	5.325%	$72.5584	$72.56	$72.55	$72.60
Purchase #3	$45.78	4.386%	$47.7879	$47.79	$47.80	$47.80
Purchase #4	$57.76	4.597%	$60.4152	$60.42	$60.40	$60.40
Purchase #5	$189.47	4.802%	$198.5683	$198.57	$198.55	$198.60
Purchase #6	$133.46	10.109%	$146.9515	$146.95	$146.95	$147.00
Purchase #7	$169.98	10.122%	$187.1854	$187.19	$187.20	$187.20
7 purchase totals =	$719.94		$772.5641	$772.58	$772.55	$772.70